Damaged a $100 side milling blade, help...

[Handlobraesing]

I managed to snap off a tooth on a 2 3/8" titanium nitride coated HSS side milling blade. I've had that happen on the tip of a drill bit, but unlike a drill bit, this blade is $100 a pop and I want to figure out what caused it so I don't destroy it. I think I can get away with one tooth missing, but if I lose anymore, I'm afraid it's going to have to be replaced.

It has cutting edges on the tip and the beveled side on the right. It suddenly grabbed the material I was milling, stalled the machine and clipped a tooth.

Any idea what I might have done wrong, or is this something that's gonna happen no matter what?

 

[Atomic_Chicken]

Greetings!

Too high a feed rate. Slow down the speed you're feeding the cutter into the material.

Best wishes,
Bawko

 

[Handlobraesing]

Greetings!

Too high a feed rate. Slow down the speed you're feeding the cutter into the material.

Best wishes,
Bawko

I wasn't really even pushing it. I was slowly bringing the material to it and right as it touched the blade, BAM!

 

[Atomic_Chicken]

Greetings!

If you're not feeding the material too fast, the other possibility is that the material is not clamped rigidly enough.

Best wishes,
Bawko

 

[highorder]

that cutter will still function with 60% of its teeth. mind you, you will have to grind/ stone the broken sections, and slow the feedrate further.

 

[Anglepoise]

Were you feeding in the right direction.
Your comment " It suddenly grabbed the material I was milling," lead me to think that might be the case.

 

[Handlobraesing]

Yes. To cut in, you push straight in. To mill to the side, you move the material to the left, pressing against the right side of the blade.

I've been doing the same all along, but it grabbed and messed up just this one time.

 

[jayb79]

Climb milling or conventional?
Climb milling is when the cutter could pull the material into the cutter, this is not recomended on manual machines but it is normal for CNC machines.
What is the material you are cutting?

 

[Handlobraesing]

Climb milling or conventional?
Climb milling is when the cutter could pull the material into the cutter, this is not recomended on manual machines but it is normal for CNC machines.
What is the material you are cutting?

Material is brass alloy. I don't know what sorta of milling, but the blade rotates downward and the material is pushed perpendicular into the blade and moved parallel with the axle.

 

[sawlight]

Trying to take too much material in one pass, not a rigid enough setup, not a rigid enough machine all come to mind. Ussually when you are climb cutting on a conventional machine you will break the whole cutter off, not just a tooth, but stranger things have happened.

Conventional cutting is running the cutter and throwing the chips into the cut, climb cutting is throwing the chips away from what has been cut. What happens on a Bridgeport type machine, is there is enough slack in the leadscrews that it is always "jumping" into the cut, not feeding steady. On a CNC machine the servomotors can compensate for this fast enough it's not a problem, we humans cannot!
Hope that helped at least some.

 

[jayb79]

Do the chips from the cut go in front of the cut of do they come out behind the cut?
here is good place to get some info on feeds and speeds http://www.niagaracutter.com/techinfo/millhandbook/index.html . Cutting brass should be very easy as long as it is a rigid setup.

 

[sawlight]

Brass is very misleading to cut, yes it is soft, but it is very "grabby". You get it in you're head you can take a lot off in one pass, but if you are not set up rigid enough, it wll "pull" the cutter right in to the material!

 

[will]

Brass is a grabby kind of material. ( if you ever tried to drill brass - the drill gets sucked into the brass ) We used to reduce the angle of the cutting edge to reduce the grab. Conventional milling is probably a better way to work this.

 

[dom]

As others have said -sounds like you were climbmilling with an unlocked table.
Start at the outside of the job if possible in the conventional milling position -this will stop any grabbing of the workpiece.
If you have to plunge into the job -lock the table and pull up the slack on the handle in the conventional milling direction -when you are to your depth -move the handle in the same direction.

If you HAVE to climbmill -keep the table locked just enough so you can still move it -this should stop or slow any workpiece grabbing

Cheers
Dom

 

[Luna]

I'd tig that sucker with a hardfacing wire and hone to shape with a diamond file.

 

[highorder]

there goes the temper...

just stone the tooth out and move on.

 

[guntotin_fool]

or consider having a professional sharpening service braze on a new tooth, commonly done with carbide teeth on saws and cutters,

 

[Luna]

there goes the temper...

just stone the tooth out and move on.

If anything I'd worry about chatter more than temper but that is just me since I'm not afraid of doing a home HT if necessary.


If it is of concern (and not always should it be) and you don't have the facilities to retreat the tool, you can find a laser welding station(like used by jewerly repair shops). These are amazing, you hold the item in your hands and weld in an Ar enclosure. Even a mall here has one for repair.

 

[scott.cr]

I agree with the above posts that milling unknown brass alloys can be tricky. I've heard lots of theories about why they break tools, but it's surprising what kind of tooling you can lose to a soft material like brass. I've also broken a few tools on those gummy hardware store aluminum angles.

BTW, use of a tapping fluid on those gummy metals is a huge help, like Rapid Tap, and don't be stingy with it. ;-)